Circuit interrupter



Jan. 7,1941. J. B. MaoNElLL cIncuIT INTERRUPTER Filed Nov. 1, 1938 2Shgets-Sheet 1 INVENTOR t/b/.yfff/l ATTORNE wlTNEssEs: @97m 75" M Jan.7, 1941. .1. B. MacNElLL CIRCUIT INTERRUPTER Filed Nov. 1, 1938 2Sheets-Sheet 2 Patented Jam?, 1941 PATENT j OFFICE f '2.221.507 cmcmrmaxaman .101m s. Mmmm. wnkimbmr, rs., mmf u ufaotnring UNi'rED vsTA'rlasWestinghouse Electric t Man pany, East Pittsburg ."ennsylvania .Oom-Pa., a corporation of Application November l, 1938, Serial No. 238,122

20 (Halma.v (Cl. 20o-146) u The arc produced by the interruption of thecircuit is flrst established between the arcing contacts and thentransferred to arc transfer horns. Froin the horns it is drawn into achamber where it isbrokenupand deio In circuit in'terrupters constructedin accordance with the teachings of the prior art, of which I a'm aware,the engagementbetween the arcing contacts is of the butt type. That isto say. the the arcing contact surfaces, when the circuit is closed.engage ina single plane perpendicular to the direction of-current flow.Butt arcingcontacts operate satisfactorily in cases in which the currentto be interrupted and .the potential at which the interruption takesplace is of moderate g magnitude. 'Wherel relatively'highvinterruptingcapacity, such as is now encounteredin many generating is involved, 1have found the circuit interruptor ofthe-prior art to be totallyinadequate.

n In a particular case an interrupting capacity of 900,000 kllovoltamperes at l5 kilovolts was required. Numerous-experiments were carriedout in an endeavor to required interruptins capacity with the circuitinterrupters of the 35 prmrart. ywnue incertain cases moderate successwas achieved, the results were on the whole unsatisfactory. lTheprincipal ydinlcu'lty which was encountered in theattempted-use of theprior art circuit breakers was that the arcing contacts .o failed to'localize the arc inthe region of the horn towhichit wastobe transferred.Inmany cases the arc was ignited in regions in the circuit breakerapparatus Awhere it could not possibly be It is, accordingly', a generalobject of my invention to provide a circuit'interrupter having highinterrupting capacity of the order of aty least' 900,000 kilovoitamperesat i5 kilovolts. Another object of my invention is to provide an 50 aircircuit lnterrupter'for interrupting high cur--` rent at mtstsngmpotentials in which the am provide an arcing contact arrangement for anair circuit interrupter such that the transfer of the arc into theextinction chamber and its extinction shall be expedited.

My invention arises from a detailed analysis of the operation of acircuit interrupter and of the demands made upon it by the circuit to beinterrupted. It is based on the realintion, as an outgrowth of theinvestigation, of the principal causes for thefailure of the arc to belocalized in the desired region; A primary condition imposed on acircuitLbreaker is that it shall prevent the flow of over-currents orshort circuit currents for any appreciable length of time. Theinterrupting elements of a vcircuit breaker must. therefore, operate ata relatively high speed. For the current and voltage involved in thepresent situation,

ythe time required for the contacts to reach a full `open positionshould be not more than .l second or 6 cycles of the 60-cycle frequencymost often encountered. 'Ihe time required for both pairs of cbntactstopart should be at most 3.5 periods of the 6 periods. Of the 3.5 periodsthe opening of the current carrying contacts vconsumes of the order of3.3 periods and the opening of the arcing contacts .2 period or .0033second. It is the last mentioned short interval o! time which is thesource of the principal difficulty arising in the use of butt arcingcontacts'.

During normal closed circuit operation both the arcing contacts and thecurrent carrying contacts are closed and the current divides itselfbetween them, a greater portion flowing through the current carrying,contacts since the resistance between the .arcing contacts is relativelyhigh. When the circuit is being opened, therel is a rush of current tothe arcing contacts at the instant at which the current carryingcontacts are Just opened. However, at the same time a small potentialdifference remains between the latter contacts and a small spark isproduced between them.

The arcing contacts should now yremain. closed until the spark isextinguished. i. e.. of the order of .2period.Ifthishappenathearcislocaliaed at the arcing contacts and is properlydrawn into the extinction chamber. The difficulty with the prior artcircuit breakers is that in their operation this desirable conditiondoes not exist.

When the current carrying contacts are iust opened andeven while theyare opening, the sudden rush of current tothe 'arcing contacts producesa mag'ne lc'force causing the arcing contacts to be blo open before theyshouldbe opened in normal operation. The arcing contacts thus openbefore' the spark between the current carrying contacts has beencompletely extinguished and the result is that the arc instead of beingignited between the arcing contacts is actually ignited between thecurrent carrying contacts. Since there is no provision in the circuitinterrupter for extinguishing the arc in the region of the currentcarrying contacts, it continues to burn and eventually not only are thecontacts destroyed but the apparatus in the circuit which is beinginterrupted is materially damaged.

It is seen from the foregoing analysis that the solution of the problemwhich arises here involves the prevention of the premature opening ofthe arcing contacts. It will be noted in solving this problem, theintroduction of a substantial delay between the opening of the currentcarrying contacts and the opening of the arcing contacts is notpracticable in view of the fact that the interrupter must be completelyopened in a short time. It is the sequence of the operations which mustbe maintained and timed, and the proper sequence can only be attained ifeach operation occurs at precisely the instant that it should occur andnot prematurely.

To obtain the desired timing of the operations, I provide cooperativearcing contacts which are with certainty prevented from openingprematurely. One of the arcing contacts is of the iinger type and clampsthe other the more tightly as the current in the region of theengagement of the contacts increases. The arcing contacts can,therefore, only open when receiving the proper impulse from thereleasing mechanism. The electromagnetic stresses in the region of thecontacts are large at the instant that the arc is ignited since thepower interrupted is high. Hence after the arc .has been ignited it mayhappen that under the enormous electric and magnetic nelds it is drawnto parts of the apparatus where its presence is undesired. To suppressthis undesired condition, the arcing contacts are, in accordance with myinvention, of a form such that the current flow at the point of nnalinterruption is in a loop convex towards the adjacent arc horn. Thetendency of the arc in such a loop is to increase in its radius ofcurvature and, therefore, the arc moves towards the arc horn and isquickly transferred thereto. In accordance with a further aspect of myinvention, the arc uhorn adjacent to the arcing contacts is moreoverdisposed as closely as possible to the point at which the arc is formed.To attain this desideratum the are horn is slotted in a directionparallel to the planes of the engaging surfaces of the fixed and movablearcing contacts and the moving arcing contact penetrates into the slotwithout engaging its sides.

'I'he novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and its method of operationtogether with additional objects and advantages thereof will best beunderstood from the following description of a specific embodiment whenread in connection with the accompanying drawings, in which:

Figure 1 is a view in front elevation, partly in section, of a circuitinterrupter constructed in accordance with my invention,

Fig. 2 is an enlarged view in side elevation of the contacts of thecircuit interrupter shown in Fig. 1, and

Fig. 3 is a plan view of the contacts shown in Fig. 2.

The apparatus shown in the drawings comprises an arc extinguishingchamber 5 formed between composite metallic uprights 1 and 9 and coversIlot insulating material secured to the uprights. Each upright 1 and 9consists of a channel beam I3 with transverse plates l5 welded to theedges of the lower opening in the channel.

The transverse plates I5 have a total width less than that of thechannel and longitudinal plates |1 extend from the inner edges of thetransverse plates forming between them an elongated opening of smallerwidth thanthat of the channel. 'Ihe web of each channel is provided withopenings near its four corners and with a central opening. Through thecorner openings insulating bars l5 of phenolic condensation materialpass and on them the plates 2| whereby an arc is broken up anddeionized, are stacked. Cylindrical insulators 33 and 24 abut thecentral openings and a conducting bar 25 passes through the openings andthe insulators.

The deionizing stack 2| is of the usual structure comprising verticaliron and copper plates with iish paper insulating sheets between them.One form of such a deionizing stack is shown in Slepian Patent No.1,927,904, issued September 26, 1933, and it will not be describedherein detail.

Ihe longitudinal plates I1 extending from the channels 3 rest on baseblocks 21 to which they are secured. The openings in the channels I3face-away from the deionizing stack 2| and cover plates 29 are providedfor these openings and the coextensive opening between the plates l1.The channels |3 and the coextensive plates i1 thus form flues throughwhich the gases generated on the interruption of a circuit areexhausted.

The fixed current carrying contact assembly 3| and lthe ilxed arcingcontact assembly 33 are mounted in a box-shaped casting 35 which issupported below the left-hand upright 1 on parallel columns 31. Thelatter columns are preferably composed of a phenolic condensationmaterial. The upper ends of the columns 31 engage lips 39 projectingfrom the casting 35 and the lower ends are secured to a suitablesupporting frame 4I. The columns 31 are held laterally by blocks 43 and45 bolted respectively to the casting 35 and the frame 4|.

A large double walled beam 41 in the form of a right angle, with thewall spacing equal to the distance between the columns 31, is supportedby the columns 31 and by a pair of short columns 4I of similar material.The angle 41 is disposed with its sides 5| and sa horizontal andvertical respectively. 'I'he horizontal sides 5| are secured at the endsto the centers of the long columns l1 and the short column 49 passesthrough the apex of the angle and engages lips 54 projecting from thevertical sides 53. The vertical sides 53 of the angle are coextensivewith the column 49. 'The columns 31 and 49 and the angle 41 are heldlaterally by blocks 55, 51 and 59 which are bolted to the parts to whichthey are secured.

The horizontal sides 5| of the angle 41 serve as bearing supports forthe pins 6| and 53 which carry at their centers the movable contact arm5l and the spring 51 whereby the arm is actuated. The pins 5| and 53 arerotatable in their bearings and the arm 55 and spring 51 may pivot aboutthe axes of the pins. The width of the horizontal side 5| .of the angle41 is such that the vertical side 53 is coextensive with the righthandupright 9 of the arc extinguishing assembly 5.

The uprights 1 and 9 rest on the casting 35 and on the vertical sides 53of the angle I1. For

this purpose, a slab 89 is secured to the Aupper ends of the verticalsides 53. The slab 89 is fastened to the right-hand block 21 and thussupports the right-hand upright 9. The left-hand block 21 rests on aninsulating washer 1| sup-y ported on a horizontal projection 13extending from the casting 35. Below the projection 13 a secondinsulating washer 15 is provided and the projection is secured to theblock 21 by a bolt 11 extending through the washers and the projectionand insulated from the projection by a sleeve 19.

From the upper surface of the casting 35 and from the slab 89 extendstuds 8| and 83 respectively, which are adjustable in height. Compositeboards having internal insulating faces 85 are supported on the studsand secured to horizontal studs 81 projecting on both sides from theupright plates I1. A chamber extending from the deionizing stack 2| tothe circuit interrupting contacts 3|, 33 and 89 and 9| is thus formedbetween the boards. The arc is moved through the chamber into thedeionizing stack 2|.

The specific structure of the arc chamber does not concern the presentinvention. However, briefly, its walls are composed internally of brousinsulating material 85, in which inserts 93 of a. refractory insulatingmaterial are disposed, and externally of iron (not shown). In Fig. 1 theinterior surface 85 of a single wall is shown. The other wall is ofsimilar structure but has been removed for the purpose of showing theinterior of the chamber.

Within the arc chamber arc transfer horns 95 and 91 are provided. Thehorns are secured to the channels I3 and tothe plates I1 coextensivewith the channels, the left-hand horn 95 being fastened to studs 99which project outwardly from the faces of the left-hand plates l1. Thetip of the left-hand horn is located immediately adjacent to thecontactterminals |03 of the ilxed arcing contact assembly 33.

The ilxed current carrying contact assembly 3| is of composite structurecomprising a pair of contact terminals preferably composed of silverplated copper. The ends of the terminals |05 are slotted and in theslots (not shown) flexible shunts |01 composed of thin ribbons of copperare fastened, preferably by sweating. At the other ends, the shunts arebolted to a tail projection |09 integral with the casting 35. The fixedarcing contact assembly 33 is of similar composite structure comprisinga pair of contact terminal elements |03 slotted at their ends. The

yslots receive the strandsof the shunts ||3 |03 and |05 may pivot in adirection perpendicular to their faces about the pins. Ihe blocks ofeach pair of terminals are urged into engagement with each other bysprings I9 wound on pins 2| extending through the walls of the4 casting35, through the terminal blocks transverse to their sides. Theengagement between the pins |2| and the blocks of the terminals |03 and|95 ,is loose so that the blocks may slide along the pins. The pins |2|are' secured to the walls of the casting and the springs ||9 rest inrecesses |23 in the walls engaging the walls on the one hand and thesides of the terminal blocks on the other. The fixed current carryingand arcing terminals |05 and |03 arethus of the slotted or finger typewith the walls of the slots or fingers resiliently urged into engagementwith each other.

The fixed arcing terminal |03 is' composed of blocks of silver-platedcopper, each ,of which is provided with inserts |25 and |21 ofsilvertungsten alloy. The alloy is arc resistant and, therefore, is notdeteriorated by the arc generated at the terminal.

The movable contact assembly 95 is of composite structure consisting ofa heavy steel support |29 to which a copper contact carrier |3| issecured. Near the upper end of the carrier `|3| the movable'arcingcontact 89 projects; the mov.. able current carrying contact 9| isparallel to the contact 89 from a position below the latter. The movablecontacts 89 and 9| are of the knife type adapted to be engaged and heldfirmly by the resiliently pivoted blocks making up the correspondingfixed terminals |03 and |05.

The movable current carrying contact 9| is composed of silver platedcopper and is prefer-l ably attenuated at its end |33 so as to limit thespace necessary for the contacts when in engagement. The movable arcingcontact is similarly attenuated at its end |35 and in the attenuatedregion is provided with inserts |31 and |39 of the arc resistant silvertungsten alloy.

The fixed arcng contact terminal |03 projects into the arc space -5 and,as has been-explained, is adjacent to the tip |0| of the left-hand arctransfer horn 95. So as to expedite the movement of the are into the arcspace, the horn 95 is slotted near its tip |0| and the movable contact89, when the circuit breaker is in the closed position, penetrates intothe slot ill.

The movable contact assembly is actuated by a rod |43 which may be movedin the usual manner by an electromagnetic system. The specific movingstructure is not shown as it does not concern the present invention. Ingeneral, the rod |43 is pivotally connected tothe actuating system atits lower end |45. At its upper end |31 the' rod engages the commonmovable pivot pin |49 of a pair of sets of toggle arms |5| and |53. Theformer set |5| pivots about a fixed pin |55 secured to the verticalsides 53 of the angle 41 and the other, |53, about a pin |51 in thesteel support |29 of the movable contact assembly 55. Below the lattervpivot pin |51 the circuit opening spring 61 is secured to pivot pin |59.The movable contacts 89 and 9| are disengaged from the xed contactterminals |03 and |05, respectively, by the action of the spring 51`when the mechanism whereby the rod |43 is moved into and held in theclosed position is released. In open- -ing the movable contact assembly65 strikes against a shock absorbing stud |6| and thus is not damaged.

I When the circuit interrupter is in the closed position, the current isprimarily carried'by the current carrying contacts 9| and 3| since theresistance between the arcing contacts 89 and 33 is relatively high. Thecurrent carrying contacts and the arcing contacts are so positioned intheir respective supportsthat when the circuit breaker opens the currentcarrying contacts 9| and |05 are first disengaged and then the movablearcing contact 89 is disengaged from the flxeu arcing fingers |03. Anarc is, therefore, produced between the latterelements. When the currentcarrying contacts are opening, the current in each of the arcing fingers|03 is increasing. Since the current paths through the fingers areparallel and in the same direction, the effect of the resultantincreasing magnetic fields is to cause theflngers to hold the fixedcontact l! more tightly until the moment for release as determined bythe moving mechanism arrives. 'Ihe establishment of an arc at thecurrent carrying contacts and Il! by reason of the opening of the arcingcontacts Il and |05 only a very short fixed interval after the openingof the currenti'carrying contacts is thus entirely precluded. I

The fixed inserts |21 in the arclng contact terminal |03 are in the formof tips extending upwardly towards the tip Ill of the arc horn I5. Thefixed arcing contact assembly I3 is moreover so disposed in the casting35 that the direction of the current ow in it between the region ofseparation of the contacts and the point of connection of the line atthe instant of interruption is first at a small angle to the horizontaland, as the point of interruption is approached, at an angle rapidlyapproaching the vertical. The insert |39 of the cooperative movablecontact I0 is also in the form of a tip so positioned that it engagesthe inserts |21 when the contacts 80 and |03 are last in engagementduring the opening operation. 'I'he contour of the'inserts |21 and Il!is such that at the point of final disengagement, the sides of theinserts |21 and i form an acute angle having its apex at the extremeupper region of the contacting surfaces, the apexbeing also the point oflast engagement of the contacts. It happens, therefore, that in theregion of separation of the arcing contacts the current flow is in asharp loop convex towards the tip IUI of the adjacent arc transex' hornQI. For this reason when the arc is produced, it also is in a sharp loopconvex towards'the tip Ill as shown in Fig. 2, and since theelectromagnetic effect of current flowing in a loop is to increase theradius of curva.V ture of the loop, the arc produced decreases itscurvature towards the tip |0| vand is quickly transferred to the hornI5.

By the transfer of the arc to the horn l5, an inductance loop is closed.The loop consists of vertical straps |63 extending betweenthe projection13 of the rod 25 passing through the insulator 23, vertical straps |65extending from 'the remaining end of the rod 2l, a pair of rods |61extending from the lower ends of the straps |85 outside of the arcchamber 5, metallic strips |09 extending from the remaining ends of thelatter rods |01 to the lugs 99 to which the arc transfer horn IIadjacent to the' fixed arcing contact I3 is secured. When the arc istransferred to the horn, a circuit is completed through this loop whichextends from the line connection to the i'ixed contacts 2| and 33through the strapsi, the bar 2i, the straps |65, the rods |01, the stripI, the arc horn $5, the movable contact assembly tl to the other lineconnection. By the action of the inductive loop, the arc is nowtransferred to the other arc horn 91. Since the latter horn is connectedto the right angle 41, the circuit through the inductive loop is notbroken and the movement of the arc continues upward until it passes intothe deionizing assembly and is extinguished.

Although I have shown and described certain specific embodiments of myinvention, I am fully aware that many modifications thereof arepossible. My invention, therefore, is not to be restrictof the castingl5 and the adjacentv end A edexcept insofar as is necessitated by theprior art and by the spirit of the appended claims.

I claim as my invention:

l. A high voltage air circuit breaker having an interrupting capacity ofat least 60,000 amperes comprising fixed land movable contact meansthrough which the current passes when the circuit is closed, a chambercontaining arc extinguishing means, mean.; including an arc-transferhorn for drawing an arc into said chamber, and additional nxed andmovable contact means disengaged after said first named contact meanswhen the circuit is being opened, said additional contact meanscomprising a pair of cooperative elements one of which is in the form ofa slot into which the other penetrates engaging the sides of the slotilrmly when the circuit is closed, said cooperative elements havingportions nearest said chamber and arc-extinguishing means whichdisengage last on opening of the circuit, and said horn extending to apoint immediately adjacent to the region in which said additionalcontacts are last engaged when the circuit is being opened and betweensaid region and said chamber.

2. Circuit interrupting apparatus comprising fixed and movable contactmeans between which an arc is ignited when the circuit is interrupted, achamber containing arc extinguishing means, and means including an arctransfer horn for drawing said arc into said chamber, said horn beingdisposed adjacentto a portion of said fixed and movable contact meanswhen they are in engagement and between said chamber and said portion,said portion comprising cooperative contact elements one of which is inthe -form of a slot into which the other penetrates engaging the wallsof the slot firmly when the circuit is closed,

said elements being so disposed on said contact means that they aredisengaged last when a circuit is being opened, the walls of said slotnear said horn being formed with tips extending toward said chamber, thecooperative element being provided with a tip at a point such that saidlast mentioned tip and the tips on said wall are disengaged last whensaid circuit is being opened and said contact means being so arrangedthat Just before the contacts part the current flow in the region oflastA engagement is in a loop convexed toward said chamber.

3. Circuit interrupting apparatus having an interrupting capacity of theorder of 900,000 kilovolt amperes at 15 kilovolts and operating tocompletely open a circuit in an interval of time of the order of .10second comprising nxed and movable contact means between which thecurrent is transferred when the circuit is closed, a chamber containingarc extinguishing means, means including an arc-transfer horn fordrawing an arc into said chamber, and additional fixed and movablecontacts disengaged after said first named contact means when thecircuit is being opened and through-which the current is shunted uponseparation of said flrst-named contact means, said additional contactscomprising a pair of cooperative elements one of which is in the form ofa slot into which the other penetrates engaging the sides of the slotfirmly when the circuit is closed, the sides of said slots beingprovided with tips extending towards said chamber and the othercooperative element of the pair being provided with a tip, said tipsbeing so arranged that they are in engagement last when said circuit isbeing opened and said additional contacts being so arranged that thecurrent flow in the region of saidI tips when the circuit is beingopened is in a loop escaso? S convexed toward said chamber, and saidhorn extending to a point immediately adjacent to the region in whichsaid additional contacts are last engaged when the circuit is beingopened and between said region and said chamber.

4. A- high voltage air circuit breaker having an interrupting capacityof at least 60,000 amperes comprising xed and movable contacts inengagement with each other over a substantial area when the circuit isclosed, means for disengaging said' contacts, the disengagement of thecontacts being a gradual operation starting in one region of saidcontacts in engagement and ending with the ignition of an arc aninterval of time of the order of .05 second later in another region ofsaid contacts, one of the contact means in said other region being inthe form of a slot into which the other penetrates engagingthe walls ofthe slot firmly when the circuit is closed, a chamber includingarc-extinguishing means, means including an arc transfer horn fortransferring said arc into said chamber, said arc transfer horn beingdisposed immediately adjacent said other region of said contacts, andmeans for causing l said arc to be transferred from one said contacts insaid other region to said horn and from said horn to said chamber.

5.i Circuit interrupting apparatus comprising fixed and movable contactsin engagement with each other over a substantial area when the circuitis closed, means for disengaging said contacts, the disengagement of thecontacts being a gradual operation starting in one region of saidcontacts in engagement and ending with the ignition of an arc aninterval of time of the order of .05 second in another region of saidcontacts, one of the contacts in said other' region being in the form ofa slot in to which the other penetrates engaging the walls of the slotfirmly when the circuit is closed, a chamber including arc-extinguishingmeans, means including an arc transfer horn for transferring said arcinto said chamber, said arc transfer horn being disposed immediatelyadjacent said other region of said contacts and having a slot thereinpenetrated by said other contact in said other region when said contactmeans are in engagement, and means for causing said arc to betransferred from one said contact means in said other region to saidhorn and from said-horn to said chamber.

6..An air circuit breaker comprising current carrying contact means, achamber including arc extinguishing means, an arc transfer horn fortransferring an arc into said chamber, means for localizing the arcgenerated by the interruption of a circuit in the region of said hornincluding arc ing contact means, incorporating a slot-shaped contactelement and a cooperative contact element which penetrates saidslot-shaped element and engages the walls of the slot when the circuitis closed, said contact 'elements having portions disposed immediatelyadjacent said horn which disengage last during opening of the circuit,and means for opening said current carrying contact means and,an`interval of vtime of thelorder of .003 second after said currentcarrying contact means have opened, opening said varcing contact means,and means for lcausing the arc generated at said arcing contacts andtransferred to said khorn to` be transferred from said horn. ito saidchamber. I

7. Apparatus according 'to claim 6 characterized by the fact that thehorn is disposed between the arcing contacts and the chamber and the cojoperative contact elements are so shaped that the current now at theinstant of interruption at said elanents is convexed towards said hornand said chamber.

8, Circuit interrupting apparatus having an interrupting capacity of theorder of 900,000 kilovolt amperes at 15 kilovolts comprising a ilxedcurrent-carrying contact of the finger type, a movable current-carryingcontact of the knife type to engage said fixed contact, a chambercontaining arc'extinguishing means, an arc transfer horn for moving anarc into said chamber, means for localizing the arc generated by theinterruption of a circuit inthe region of said horn including a fixedarcing contact of the finger type disposed adjacent to said horn, amovable arcing contact of the knife type to engage said fixed arcingcontact when said circuit is closed, said arcing contacts havingportions nearest said horn which disengage last upon opening of thecircuit, and means for opening said current carrying contacts and,aninterval of time of the order of .003 second after the opening of saidcurrent-carrying contact, opening said arcing contacts, and. means fortransferring the arc ignited by the opening of said arcing contacts andtransferred to said horn from said horn to said chamber.

9. Circuit interrupting apparatus comprising a fixed current-carryingcontact of the finger type, aimovable current-carrying contact of theknife type to engage said fixed contact, a chamber containing arcextinguishing means, an arc transfer horn for moving an arc into saidchamber, means for localizing the arc generated by the interruption of acircuit/in the region of said horn including a xed arcing contact of thelinger type disposed adjacent to said horn, a movable arcing contact ofthe knife type to engage said fixed arcing contact when said circuit isclosed, said movable arcing contact penetrating said horn and said hornbeing slotted to receive said arcing contact, and means for opening saidcurrent-carrying contacts and, an interval of time of the order of .003

, second after the opening of said current-carrying contacts, openingsaid arcing contacts, and means for transferring the arc ignited by theopening of said arcing contacts and transferred to said horn from saidhorn to said chamber. y

10. Circuit interrupting apparatus comprising a xed current-carryingcontact, a movable currentl carrying contact tov engage said fixed con-4tact, a chamber containing arc extinguishing circuit is closed, saidmovable arcing contactY penetrating said horn and said horn beingslotted to receive4 said arcing contact, and means for open-ingsaidcurrentl carrying contacts and immediately thereafter opening saidarcing contacts,

1l. Circuit interrupting apparatus comprising-af xed current-carryingcontact of the ingerptyp'e's" a` movable current-carrying contactofthe-knife type to engage said fixed contact, a chamber corr--A tainingarc extinguishing means, an arc transfer?. horn for moving anarc intosaid chamber, means for localizing the arc generated by the interrupfktion of a'circuit in the'region of, said horn includ-- ing a ilxedarcing contact of the finger type dis-I posed adjacent to said horn, amovable arcingl contact of the knife type to engage said fixed arcingcontact when said circuit is closed, said arcing contacts havingportions nearest said horn which disengage last upon opening of 'thecircuit, and means for opening said current-carrying contacts and, aninterval of time of the order of .003 second after the opening of saidcurrent-carrying contact, opening said arcing contacts, and'means fortransferring the arc ignited by the opening of said arcing contacts andtransferred to said horn from said horn to said chamber.

12. Circuit interrupting apparatus comprising fixed and movable contactmeans in engagement with each other over a substantial area when thecircuit is closed, means for disengagini said contactmeans, thedisengagement of the contact means being a gradual operation starting inone region of said contact means in engagement and ending with theignition of an arc in another region of said contacts, one of thecontact means in said other region being in the form of a slot intowhich the other penetrates engaging the walls of the slot firmly whenthe circuit is closed, a chamber including arc-extinguishing means,means including an arc transer horn for transferring said arc into saidchamber, said arc transfer horn being disposed immediately adjacent saidother region of said contacts and having a slot therein penetrated bysaid other contact in said other region when said contact means are inengagement, and means for causing said arc to be transferred from onesaid contact means in said other region to said horn and from said hornto said chamber.

13. In a circuit interrupter, fixed contact means comprising a pair ofpivoted finger contacts, a pair of flexible shunt conductors connectedto" said finger contacts, said finger contacts being biased towards eachother by the parallel current ow through said finger contacts when theinterrupteris closed, a cooperating movable knife contact firmly engagedon opposite sides byv said finger contacts when theinterrupter isclosed, means forming a chamber containing arc-extinguishing means, saidcontacts having portions disposed nearest said chamber which disengagelast when the circuit is opened, and means including an arc transferhorn for drawing an arc into said chamber and extinguishing means, saidhorn being disposed immediately adjacent the portions of said contactswhich disengage last and between said chamber and said portions of thecontacts.

14. In a circuit interrupter, fixed contact means comprising a pair offinger contacts, a cooperating movable knife contact firmly engaged on.op.- posite sides by the finger contacts when the interrupter is closed,Ameans forming a chamber containing arc-extinguishing means, said fingercontacts and knife contact having portions nearest said chamber whichare disengaged last on opening of the circuit, and means including anarc horn for drawing the arc into said chamber and extinguishing means,said arc horn being disposed immediately adjacent the portions of saidcontactswhich are last disengaged and between said arc-extinguishingmeans and said portions of said contacts.

15. In a circuit interrupter, fixed contact meansl comprising a pair ofnger contacts, a cooperating movable knife contact posite sides by thefinger contacts when the interrupter is closed, means forming a chamberlcontaining arc-extinguishing means, said contacts having tipsnearestsaid chamber andarcfirmly engaged on opextinguishing means whichare disengaged isst on opening of the circuit, and said contacts andtheirtipsbeingarrangedsothatthecurrentiiow when the circuit is beingopened is in a loop convexed toward said chamber, and means including anarc horn for drawing the arc into said chamber and extinguishing means,said arc horn being disposed immediately adjacent the tips of Asaidcontacts and between said arc-extinguishing means and said tipsof thecontacts.

16. In a circuit interrupter, fixed and movable main contact means,additional contact means through which the current is shunted upon sepration of said main contact means, said additional contact means beingdisengaged after said main contact means when the circuit is opened andcomprising a pair of finger contacts and a cooperating movable knifecontact firmly engaged on opposite sides by said finger contacts, meansforming a chamber containing arc-extinguishing means, said fingercontacts and said knife contact having tips nearest said chamber andarcextinguishing means which are disengaged last upon opening of thecircuit, said contacts being arranged so that the current now in theregion of the tips when the circuit is being opened is in a loopconvexed toward the chamber and srcextinguishing means, and meansincluding an arc transfer horn for transferring the arc into saidchamber and arc-extinguishing means, said are horn being disposedimmediately adjacent the tips of said contacts and between saidsrc-extinguishing means and said tips.

17. In a circuity interrupter, stationary contact means comprising apair of main nnger contacts, a pair of arcing finger contacts, and scooperating movable knife contact firmly engaged on opposite sides bythe finger contacts, said knife contact being adapted to separate fromsaid main nnger contacts before separating from said arcing fingercontacts, means forming a chamber containing arc-extinguishing means,said arcing nnger f contacts and the cooperating portion of said knifecontact having tips nearest said chamber and arcextinguishing meanswhich disengage last upon opening of the circuit and arranged so thatthe current now in the region of the tips when the circuit is beingopened is in s. loop convexed toward the chamber and thearc-extinguishing means, and means including an arc transfer horn fortransferring the arc into said chamber and arc-extinguishing means, saidhorn being disposed immediately adjacent the tips of said contacts andbetween said arc-extinguishing means and said tips.

18. In a circuit interruptor, fixed contact means comprising a pair ofnnger contacts, s cooperating movable knife contact firmly engaged onopposite sides by the finger contacts when the inter-4 rupter is closed,means forming a chamber containing arc-extinguishing means, said fingerccntacts and knife contact having portions nearest said chamber whichare disengaged isst on opening of the circuit, and means including ansrc horn for drawing the arc into said chamber and ex means, said arehorn being disposed immediately adiacent -the portions of saidcontactswhichsr'elsstdisengsgedsndbetweensaid src-extinguishing means manid pertain or und contacts, and said are horn having a slot adjacentsaid portion of said contacts which is penetrated by the end of theknife contact when the interfrupter is closed.

19. A circuit breaker comprising opposed substantially parallel nngercontacts, s cooperating movable knife contact ilrmiy engaged on oppositesldesbysaidnngercontactswhenthebreakeris closed, a chamber containingarc extinguishing means, and means including an arc horn for drawing thearc into said chamber, said horn being disposed adjacent to said iixedand movable contacts when theyy are in engagement and between saidchamber and said contacts, said contacts having portions nearest saidhorn which are disengaged last when the circuit is being opened.

20. An air circuit breaker comprising stationary and movable maincurrent carrying contacts. auxiliary contacts through which the currentis shunted upon separation oi said main contacts,

il said auxiliary contacts being disengaged alter said main contactswhen the circuit is opened and comprising a pair ot iinger contacts anda cooperating movablerknife contact nrmly engaged on opposite sides bysaid ilnger contacts and rigidly secnred for movement with the movablemain contact, a chamber containing arc extinguishing means adjacent saidauxiliary contacts, said iinger contacts and said knife contact havingtips nearest said chamber and arc extinguishing means which aredisengased last upon opening o! the circuit, and means including an archorn for transferring the arc into said chamber, said horn beingdisposed immediately adjacent the tips of said auxiliary contacts andbetween said arc extinguishing means and said tips.

JOHN B. MACNEILL.

